Product carrying pipelines such as used for oil, gas, chemical and other liquid state transmission are installed by welding end to end multiple sections of steel pipe. Welding operations have heretofore been performed automatically as disclosed in U.S. Pat. No. 3,461,264 to Nelson et al. Previous to the availability of automatic welders, such pipes had been welded using hand methods of electrical or acetylene welding procedures.
In achieving high quality work, it has been found to be extremely advantageous to utilize automatic arc welding techniques such as disclosed in said Nelson et al, U.S. Pat. No. 3,461,264. In accordance with such techniques, the confronting ends of two pipe sections that are to be joined are suitably shaped so that when the pipe sections are brought into contact, one with another, there is formed a relatively narrow inside groove, a shallow contact band or land concentrically spaced outwardly from the inner groove, and a relatively deep outer groove. The operation had been to initially join the pipe sections together by a weld pass on the inside of the pipe to fill the inside shallow groove with weld metal. Thereafter, external welding procedures are employed using systems such as shown in U.S. Pat. No. 3,806,694 to Nelson et al. By this means, the outer groove is filled and the weld is completed.
In order to avoid the necessity for the initial inside welding pass and the attendant difficulties in operating and maintaining automatic equipment to achieve such inside welding operations, attempts have been made to achieve satisfactory welds with operations wholly outside the pipe. In connection with such attempts, backup pads have been utilized which, when placed inside the pipe, contact the inner surface of the two pipe sections at the site of the joint, thereby aiding in controlling the welding operation as it proceeds from an outside unit. Even with backup pads, however, the viscous weld metal has tended to flow downwardly under gravity as the welder circumscribed the joint. In such attempts, there has remained the persistent problem of achieving uniformity of the weld and heretofore wholly successful outside welding operations have not been uniformly achieved.